Well tool comprising a frangible well barrier, and a method for providing such a well tool

ABSTRACT

A well tool device includes a housing, a frangible disc and a seat for supporting the frangible disc in relation to the housing. The housing has an inner surface defining a through bore. The frangible disc is provided in the through bore and includes a side surface. The seat includes a side surface. A sealing device is provided between the frangible disc and the seat. The sealing device provided between the side surface of the frangible disc and the side surface of the seat is made from a vulcanized rubber material.

FIELD OF THE INVENTION

The present invention relates to a well tool comprising a frangible well barrier, and a method for providing such a well tool.

BACKGROUND OF THE INVENTION

Frangible well plugs are commonly used in tools for oil and/or gas wells. These plugs provide a pressure barrier in the tool, for example during periodic or permanent isolation of zones in the well, during well integrity testing, etc.

These frangible well plugs have a frangible barrier element in the form of a frangible disc made from glass, hardened glass, ceramics etc. The barrier element is provided in a seat in a metal housing. The barrier element may be removed by means of various techniques, where the purpose is to disintegrate the element into small pieces.

An example of a glass plug is known from NO 321 976 (TCO AS). The plug comprises a number of layered or stratified ring discs of a given thickness, which are placed in abutment on top of one another. Between the different layers of the plug an intermediate film of plastic, felt or paper is inserted; the various glass layers may also be joined by means of lamination by an adhesive such as a glue. During use the plug will be mounted in a plug-receiving chamber in a tubing, where the underside of the plug rests in a seat at the bottom of the chamber. An explosive charge is furthermore incorporated in the top of the plug by one or more recesses being drilled out from the top of the plug, in which recesses the explosive charge(s) are placed.

Another example is known from NO 20130427 (Vosstech AS). Here, the plug has one glass disc, which may be disintegrated by a radial pin or loading device being pushed into the glass disc.

Glass disks made of float glass of soda lime type are commonly used in such well plugs. Today, the highest available thickness for float glass of soda lime type of acceptable quality is produced at a maximum thickness of ca 25 mm. The maximum pressure a glass disc may withstand will depend on the glass quality and the diameter of the glass disc. Hence, this thickness of ca 25 mm represents a pressure limit for the glass plug. If the glass plug is to be used for higher pressures and higher diameters, several such glass discs must be used together in order to withstand higher pressures. The above NO 321 976 shows an example where several glass discs are assembled into one larger glass disc body.

With the above prior art well plugs, different types of seals or sealing elements are used between the metal and the glass. Often, one type of seal (typically o-ring) is used circumferentially around the glass disc to as a pressure seal to avoid fluid flow between the glass disc and the metal housing and a second type of seal or sealing element is used as a seal in the upper part and lower part of the seat to avoid contact between the glass disc and the metal housing, as such contact will cause an undesired breaking of the glass disc. A disadvantage with these prior art seals is that they require a very fine precision during machining of the metal housing and during polishing and hardening of the glass disc. Hence, it is an object of the invention to avoid or reduce the need of such fine precision machining operations.

Another disadvantage with these seals is that they are made of expensive materials, typically one O-ring, and two seat seals (upper and lower seat surface) needed for one glass disc will cost about NOK 3-5000. One object of the invention is to be able use alternative and cheaper seal materials.

Another disadvantage with the above seals is they are vulnerable to physical impacts. Hence, if a prior art well tool are falling to the ground during lifting the well tool for transportation, there is a risk for undesired breaking of the glass disk. One object of the invention is therefore to improve the support of, and the protection of, the glass disc within the seat of the well tool against physical impacts.

Another problem with the above seals is that when the frangible disc is disintegrated, the seals may follow the production flow and get stuck, in which case they may cause problems when later operations are to be performed in the well.

SUMMARY OF THE INVENTION

The present invention relates to a well tool device, comprising:

a housing having an inner surface defining a through bore;

a frangible disc provided in the through bore, where the frangible disc comprises a side surface;

a seat for supporting the frangible disc in relation to the housing, where the seat comprises a side surface;

a sealing device provided between the frangible disc and the seat;

characterized in that:

the sealing device provided between the side surface of the frangible disc and the side surface of the seat is made from a vulcanized rubber material.

Accordingly, the sealing device made from the vulcanized rubber material is replacing the o-ring(s) commonly used in prior art. In this aspect of the invention, prior art contact-preventing sealing elements may be used between the upper chamfered supporting surface of the seat and the upper chamfered supporting surface of the disc, and between the lower chamfered supporting surface of the seat and the lower chamfered supporting surface of the disc.

In another aspect of the invention, the sealing device made from the vulcanized rubber material may be used between the respective chamfered surfaces as well. In this aspect of the invention, the sealing device made from one body of vulcanized rubber material is replacing the previously known three separate sealing elements (at least one o-ring and two contact-preventing sealing elements).

One or several channels may be provided between the outside of the housing and the seat to allow excessive rubber material to escape out through the channel during the injection of the rubber material.

According to one aspect of the invention, the seat has been pre-treated before the assembly of the well tool device. The pre-treatment can be a sand-blowing process and a priming process before the assembly of the well tool device. Also the frangible disc may be pre-treated before the assembly of the well tool device. The pre-treatment can be a priming process before the assembly of the well tool device.

In one aspect of the invention, a reinforcement fiber is incorporated into the vulcanized rubber material of the sealing device.

In one aspect, the housing comprises:

a main housing section in which the seat is provided, where a section of the main housing section comprises an inwardly threaded area;

an auxiliary housing section comprising a corresponding outwardly threaded area for connection to the inwardly threaded area of the main housing section.

In one aspect of the invention, the housing comprises:

a first housing section, where a first seat section is provided in the inner surface of the first housing section;

a second housing section, where a second seat section is provided in the inner surface of the second housing section;

a third housing section provided circumferentially outside the first and second housing sections;

where the sealing device is provided continuously in an annular compartment provided axially between the first and second housing sections and radially between a side surface of the frangible disc and an inner surface of the third housing section.

The first and second housing sections may comprise a piston surface facing away from their respective seat sections.

In one aspect of the invention, an adhesive is provided between the sealing device and the frangible disc. The adhesive is typically added to the frangible disc before the injection of the rubber material.

The present invention also relates to a method for manufacturing a well tool device, comprising the steps of:

-   a) providing a frangible disc; -   b) aligning a frangible disc in relation to a seat provided in an     inner surface of a housing; -   c) providing a rubber material into a compartment provided between     the seat and the frangible disc; -   d) vulcanizing the rubber material provided in the compartment,     thereby forming a sealing element provided between the housing and     the frangible disc.

The compartment may comprise a first compartment defined as the compartments between the upper chamfered supporting surface of the seat and the upper chamfered supporting surface of the disc and between the lower chamfered supporting surface of the seat and the lower chamfered supporting surface of the disc, and a second compartment defined as the compartment between the side surface of the frangible disc and the side surface of the seat.

In one aspect, step b) comprises:

-   c1) heating of the rubber material; -   c2) injecting the rubber material into the compartment.

The step of injecting the rubber material into the compartment is performed until the rubber material is exiting through a channel provided in the housing radially outside of the seat.

In one aspect, the method comprises a step of incorporating a reinforcement fiber into the rubber material before step d).

In one aspect the method comprises a step of treating the seat with a sand-blowing process and a priming process step before step b).

DETAILED DESCRIPTION

In the following, embodiments of the invention will be described in detail with reference to the enclosed drawings, where:

FIG. 1 illustrates a cross sectional side view of the first embodiment;

FIG. 2a illustrates an enlarged view of the reinforcing fibers in an alternative embodiment;

FIG. 2b illustrates an alternative embodiment of FIG. 2 a;

FIG. 2c illustrates details of the seat;

FIG. 2d illustrates details of the frangible disc;

FIG. 3 illustrates a cross sectional side view of first step in the manufacturing of the first embodiment;

FIG. 4 illustrates an injecting molding tool used during the manufacturing;

FIG. 5 illustrates a side view of the first embodiment where two such molding tools of FIG. 4 are used;

FIG. 6 illustrates a cross sectional side view of a second embodiment;

FIG. 7 illustrates a detailed view of the third housing section in FIG. 6;

FIG. 8 illustrates a detailed view of the first and second housing sections of FIG. 6;

FIG. 9 illustrates a cross sectional side view of a further embodiment

It is now referred to FIG. 1, where a well tool device is indicated by reference number 1. The well tool device 1 comprises a housing 10 having an inner surface 11 defining a through bore 12 in the longitudinal or axial direction I through the housing 10. A frangible disc 20 is provided in the through bore 12, for preventing fluid flow through the bore until the frangible disc is disintegrated. The housing 10 is typically cylindrical, and is made of a metal suitable for the environment in the respective well.

A seat 13 is provided for supporting the frangible disc 20 in relation to the housing 10. In FIG. 1 the seat 13 is provided in the inner surface 11 of the housing 10. The seat 13 is typically provided as a widened section of the bore 12.

The frangible disc 20 is preferably a disc made of hardened glass.

The well tool device 1 further comprises a frangible disc 20 provided in the seat 13, as shown in FIG. 1.

It is now referred to FIGS. 2c and 2d . In FIG. 2c , it is shown that the seat 13 of the housing 10 comprises upper and lower chamfered surfaces C13 and a side surface A13 between the upper and lower chamfered surfaces C13. The side surface A13 is typically provided in an axial direction, i.e. parallel to the longitudinal axis I of the well tool device 1.

In FIG. 2d , it is shown that the disc 20 comprises upper and lower chamfered surfaces C20 and a side surface A20 provided between the upper and lower chamfered surfaces C20.

The purpose of the respective upper and lower chamfered supporting surfaces C20, C13 is to transfer axial fluid pressure applied by the fluid in the well bore 12 on the frangible disc 20 to the housing 10.

In FIG. 1, it is provided a first compartment 15 a and a second compartment 15 b between the frangible disc 20 and the seat 13 for the sealing device 30.

The first compartment 15 a is defined as the compartment between the chamfered supporting surfaces C20, C13. Hence, there is both an upper and a lower first compartment 15 a.

The second compartment 15 b is defined as the compartment between the side surface A20 of the frangible disc 20 and the side surface A13 of the seat 13.

In the present invention, the sealing device 30 is made from a vulcanized rubber material. The rubber material is injected or pressed into the first and second compartments 15 a, 15 b and thereafter, a vulcanizing process is performed to harden the rubber material. This injection and vulcanizing method will be described further below. As the first and second compartments 15 a, 15 b are filled with the rubber material, the rubber material will fill the available space of the first and second compartments 15 a, 15 b, and hence, the tolerances during the machining process during the manufacturing of the housing device 10 and the frangible disc 20 is no longer an important factor, as the entire space or void between the housing and disc will be filled with rubber material.

The rubber material may for example be a synthetic rubber material, selected among those materials suitable for the environment in the hydrocarbon well (i.e. dependent on temperature, pressure and amount of H2S content etc in the well). The rubber material may for example be NBR (Nitrile Butadiene rubber), HNBR (Hydrogenated Nitrile Butadiene Rubber), FKM (fluoroelastomers), FFKM (perfluoro-elastomers) or other suitable materials.

According to the embodiment in FIG. 1, the vulcanized rubber material is provided between the side surface A20 of the frangible disc 20 and the side surface A13 of the seat 13, and between the respective upper and lower chamfered surfaces C13 and C20.

In FIG. 1, a channel 15 c is shown between the outside of the housing 10 and the seat 13. The purpose of the channel 15 c is to avoid air/gas pockets in the rubber material of the sealing device 30, as air and excessive rubber material is allowed to escape out through the channel 15 c during the injection process. There might be several such channels 15 c circumferentially through the housing 10.

In FIG. 2a , an alternative embodiment is disclosed. Here, reinforcement fibers 32 are incorporated into the vulcanized rubber material. The fibers 32 are provided as three upper rings and three lower rings provided between the respective upper and lower chamfered supporting surfaces C20, C13. These rings of fibers 32 are provided in planes being perpendicular to the longitudinal axis I.

In FIG. 2b , yet an alternative embodiment is disclosed. Here, the reinforcement fibers 32 are also provided into the vulcanized rubber material, but in a more axial direction, i.e. from the upper side of the frangible disc 20, down between the upper chamfered supporting surfaces C20, C13, then down along the side of the disc 20 and then further down between the lower chamfered supporting surfaces C20, C13 to the lower side of the disc 20, as shown in FIG. 2b . Several such fibers will then be distributed around the disc 20.

In yet an alternative, the fibers 32 could be provided as short fibers mixed into the rubber material and then being injected together with the rubber material. The fibers 32 will then be distributed randomly in the rubber material.

The fibers can be made of any suitable material, for example aramid.

It is now referred to FIG. 3. Here, it is shown that the housing 10 comprises a main housing section 10 a and an auxiliary housing section 10 b. An area of the main housing section 10 a comprises an inwardly threaded area 14, and the auxiliary housing section 10 b comprises a corresponding outwardly threaded area 14 for connection to the inwardly threaded area 14 of the main housing section 10 a. The seat 13 is formed in the main housing section 10 a axially above the auxiliary housing section 10 b, where the lower chamfered supporting surface C10 of the seat 13 is provided in the upper part of the auxiliary housing section 10 b.

It is now referred to FIG. 6. Here it is shown that the housing 10 comprises a first, a second and a third housing section with reference numbers 10 c, 10 d and 10 e respectively.

The first housing section 10 c comprises a first seat section 13 a comprising the upper chamfered surface C13 of the seat 13. The first seat section 13 a is provided in the inner surface 11 of the first housing section 10 c. The second housing section 10 d comprises a second seat section 13 b comprising the lowered chamfered surface C13 of the seat 13. The second housing section 13 b is provided in the inner surface 11 of the second housing section 10 d. As shown in FIGS. 6 and 8, the upper part of the seat 13 is provided in the lower part of the first housing section 10 c and the lower part of the seat 13 is provided in the upper part of the second housing section 10 d. Here, there is no channel 15 c for excessive rubber material, instead there is an annular compartment 16 formed axially between the first and second housing sections 10 c, 10 d.

The third housing section 10 e is provided circumferentially around the first and second housing sections 10 c, 10 d. The third housing section 10 e is also provided axially above and below the first and second housing sections 10 c, 10 d. The third housing section 10 e also has a through bore 12, where the diameter of the bore 12 preferably is the same axially through the well tool device 1, as indicated in FIG. 6, where diameter D10 e=diameter D10c=diameter D10 d. The only area of the bore 12 having a larger diameter than the diameter D10 e is the area of the seat 13 itself.

As shown in FIG. 6, the sealing device 30 is provided continuously in the annular compartment 16 axially between the first and second housing sections 10 c, 10 d and radially between the side surface A20 of the frangible disc 20 and an inner surface of the third housing section 10 e (the above second compartment 15 b). It should be noted that the sealing device 30 may also be provided in the first compartment 15 a as described with reference to FIG. 1, i.e. in between the chamfered supporting surfaces (reference numbers C13 and C20 of FIG. 1). As in the embodiment in FIG. 1, the vulcanized sealing material has the function of preventing fluid flow between the upper side and lower sides of the frangible disc 20 and at the same time has the function of preventing contact between the frangible disc 20 and the seat 13 of the housing 10 when a high fluid pressure is applied to one side of the frangible disc 20 (i.e. to avoid undesired shattering of the frangible disc).

As shown in FIGS. 6 and 7, the third housing section 10 e comprises a recess 19 where the inner surface 11 a has a larger diameter (diameter D11 a of FIG. 6). The recess 19 is forming a compartment for the first and second housing sections 10 c, 10 d.

Each of the first and second housing sections 10 c, 10 d comprises a piston surface 17 facing away from their respective seat sections 13 a, 13 b, as shown in FIG. 8. Hence, when fluid pressure is increasing above the frangible disc 20 in relation to the fluid pressure below the frangible disc 20, then a positive force A will be applied to the piston surface 17 of the first housing section 10 c. This force A will apply a pressure to the vulcanized rubber material of the sealing device 30 as the first housing section 10 c may move downwardly. It should be noted that the second housing section 10 d can not move downwardly, hence, the vulcanized rubber material will be compressed. Consequently, some of the vulcanized rubber material will be pressed radially out from the annular compartment 16 and apply a pressure towards the surface 11 a of the third housing section 10 e. Hence, no fluid will be able to pass from the upper side of the frangible disc 20 to the lower side of the frangible disc 20 along the surface 11 a. Even better, if the pressure and hence the force A increases, this force will increase the axial pressure on the vulcanized rubber material which in turn will increase the sealing effect between the frangible disc 20, the first and second housing sections 10 c, 10 d and the surface 11 a of the third housing section 10 e.

In FIG. 8, it is shown that the first seat section 13 a comprises the upper chamfered surface C13 and an upper subsurface of the side surface A13, while the second seat section 13 b comprises the lower chamfered surface C13 and a lower subsurface of the side surface A13.

The well tool device 1 may further comprise a primer material or an adhesive material between the sealing device 30 and the frangible disc 20 and/or between the sealing device 30 and the housing 10, in order to improve the sealing effect of the sealing device 30.

Preferably, also the seat 13 of the housing device 10 has been pre-treated before applying primer and/or adhesive and then the rubber material to improve the sealing effect. Such a pre-treatment may for example be a sand-blowing process.

The method for manufacturing the well tool device 1 will now be described with reference to FIGS. 3, 4 and 5.

Initially, the different parts are provided, i.e. the frangible disc 20 and the housing 10, together with the rubber material for the sealing device 30. They may be pre-treated, for example by the above described sand-blowing process, priming applying process and/or adhesive applying process.

First, the frangible disc 20 is aligned in relation to the seat 13. In the aligning step, it should be ensured that there is a compartment 15 a, i.e. a first compartment, and a compartment 15 b, i.e. a second compartment, between the frangible disc 20 and the seat 13 for the embodiment in FIGS. 1 and 3. In FIG. 3, the frangible disc 20 is inserted into the bore 12 of the main housing 10 a and located in the seat 13 before the auxiliary housing 10 b is connected to the main housing 10 by means of the threaded connection 14.

In the embodiment in FIG. 6, it should also be ensured that there is an annular compartment 16 between the first and second housing sections 10 c, 10 d, in addition to the first and second compartments 15 a and 15 b. As shown in FIG. 7, there is a threaded connection 14 for the third housing section 10 e, in order to be able to insert the first and second housings sections 10 c, 10 d and the frangible disc 20 into the recess 19 of the third housing section 10 e. Accordingly, also the third housing section 10 e comprises a main housing and an auxiliary housing connectable to each other via the threaded connection 14.

In order to align the parts together, spacers or similar other means may be used to keep a distance between the parts before the injection of the rubber material.

If reinforcement fibers 32 are to be used, they are first located in the first compartment 15 a for the embodiment in FIG. 2a , and in first and second compartments 15 a, 15 b for the embodiment in FIG. 2 b.

In FIG. 4, an injection mold IM is shown, comprising a body B and injection channels IC. One such injection mold IM is provided above the frangible disc 20 and one such injection mold IM is provided below the frangible disc 20, as shown in FIG. 5. The injection channels IC are provided to guide rubber material into the first compartment 15 a.

In the next step, the rubber material is injected via the injection mold IM into the first and second compartments 15 a, 15 b provided between the seat 13 and the frangible disc 20. The rubber material is injected until the rubber material is exiting out through the channels 15 c in the embodiment of FIGS. 1 and 2. In the embodiment of FIG. 6, air and gas will exit along surface 11 a. However, it is not possible to visually observe when the rubber material is reaching the surface 11 a. Hence, the injection process may be stopped when the injection pressure reaches a predetermined pressure threshold etc.

During the injection, the rubber material and possibly also the housing 10 may be preheated for increasing the viscosity of the rubber material.

In the next step, a vulcanizing process is performed. The vulcanizing process results in an increased strength in the rubber material.

The well tool device 1 shown in FIG. 1, i.e. with a sealing device 30 made from a vulcanized rubber material, has been pressurized to 6500 psi (˜448 bar) at a temperature of 120° C.

For the above embodiments, it has been described that the vulcanized rubber material is used as a sealing device 30 both in the first compartment 15 a and also in the second compartment 15 b and hence, the sealing device 30 are serving two purposes, i.e. as a fluid seal and to prevent contact between seat of housing and disc.

It should be noted that in an alternative embodiment to those described above, the sealing device 30 made of vulcanized rubber material may be used for the function of preventing fluid flow between the upper side and lower sides of the frangible disc 20 only. This is illustrated in FIG. 9, where the vulcanized rubber material is provided in the second compartment 15 b only, i.e. the vulcanized rubber material is provided between the side surface A20 of the frangible disc 20 and the side surface A13 of the seat 13.

In such an embodiment, another material, such as prior art sealing materials may be used in the first compartment 15 a between the chamfered supporting surfaces C13 and C20 for the function of transferring axial forces from the frangible disc 20 to the seat 13 of the housing 10 and hence to avoid contact between the frangible disc 20 and the seat of the housing 10.

The well tool device 1 described herein may be a part of a plugging device, such as a bridge plug. The housing 10 will then typically be a part of the mandrel of the plugging device. The well tool device 1 may also be a part of a completion string, where the purpose of the frangible glass disc is used to pressure test the completion string, and when the frangible disc is removed, in order to start the production from the well. The housing 10 will here typically be a part of the completion string. The well tool device 1 may also be a part of other well tools where a temporary barrier is needed. 

1. A well tool device, comprising: a housing having an inner surface defining a through bore; a frangible disc provided in the through bore, where the frangible disc comprises a first side surface; a seat for supporting the frangible disc in relation to the housing, where the seat comprises a second side surface; and a sealing device provided between the frangible disc and the seat, wherein the sealing device provided between the first side surface of the frangible disc and the second side surface of the seat is made from a vulcanized rubber material.
 2. The well tool device according to claim 1, wherein the seat has been pre-treated before an assembly of the well tool device.
 3. The well tool device according to claim 2, wherein the seat has been pre-treated with a sand-blowing process and a priming process before the assembly of the well tool device.
 4. The well tool device according to claim 1, wherein the frangible disc (20) has been pre-treated before an assembly of the well tool device.
 5. The well tool device according to claim 4, wherein the frangible disc has been pre-treated with a priming process before the assembly of the well tool device.
 6. The well tool device according to claim 1, wherein a reinforcement fiber is incorporated into the vulcanized rubber material of the sealing device.
 7. The well tool device according to claim 1, wherein the housing comprises: a main housing section in which the seat is provided, where a section of the main housing section comprises an inwardly threaded area; and an auxiliary housing section comprising a corresponding outwardly threaded area for connection to the inwardly threaded area of the main housing section.
 8. The well tool device according to claim 1, wherein the housing comprises: a first housing section, wherein a first seat section is provided in the inner surface of the first housing section; a second housing section, wherein a second seat section is provided in the inner surface of the second housing section; and a third housing section provided circumferentially outside the first and second housing sections, wherein the sealing device is provided continuously in an annular compartment provided axially between the first and second housing sections and radially between the first side surface of the frangible disc and an inner surface of the third housing section.
 9. The well tool device according to claim 7, wherein each of the first and second housing sections comprises a piston surface facing away from the first and second seat sections, respectively.
 10. The well tool device according to claim 1, further comprising an adhesive between the sealing device and the frangible disc.
 11. A method for manufacturing a well tool device, comprising: a) providing a frangible disc; b) aligning the frangible disc in relation to a seat provided in an inner surface of a housing; c) providing a rubber material into a compartment provided between the seat and the frangible disc; and d) vulcanizing the rubber material provided in the compartment, thereby forming a sealing element provided between the housing and the frangible disc.
 12. The method according to claim 11, where step b) comprises: c1) heating of the rubber material; and c2) injecting the rubber material into the compartment.
 13. The method according to claim 12, wherein the step of injecting the rubber material into the compartment is performed until the rubber material is exiting through a channel provided in the housing radially outside of the seat.
 14. The method according to claim 11, further comprising the step of incorporating a reinforcement fiber into the rubber material before step d).
 15. The method according to claim 11, wherein the method comprises the following step before step b): treating the seat with a sand-blowing process and a priming process. 